Medical systems which comprise implantable parts are well known. In many cases, the implantable parts consume energy and thus have to be supplied with energy, which can suitably be done from a power source which is external to the patient's body and which uses an external energy source. In order to facilitate the supply of energy as much as possible for the patient, an implanted device can be supplied with energy from an external energy source by means of inductive transfer of energy.
Inductive energy supply is a principle which works well for implanted systems, but systems known at present are not always able to adapt the amount of energy supplied to the implanted parts as rapidly as might be desirable in some situations.